Articles of composite structures of fibrous glass



June 27, 1967 L. B. JOHNSTON ARTICLES OF COMPOSITE STRUCTURES OF FIBROUSGLASS 5 Sheets-Sheet 1 Original Filed Dec. 31, 1956.

INVENTOR:

Ian/ELL B. Imus TON.

June 27, 1967 L. B. JOHNSTON 3,328,086

ARTICLES OF COMPOSITE STRUCTURES OF FIBROUSGLASS Original Filed Dec. 31,1956 3 s f ms 2 INVENTOR! Lam/ELL B. Jmrsrm.

ATTORNEY June 27, 1967 B. JOHNSTON 3,328,086

ARTICLES OF COMPOSITE STRUCTURES OF FIBROUS GLASS Original Filed Dec.51, 1956 3 heets$heet 5 wa pg INVENTOR DWELL B. Janus TUN.

ATTORNEYS. 1'

United States Patent This application is a division of application Ser.No. 267,024, filed in the name of the present inventor on Mar. 21, 1963,now abandoned, the latter application being a division of applicationSer. No. 631,830, filed in the name of the present inventor on Dec. 31,1956 and which issued Dec. 10, 1963 as US. Patent No. 3,113,788.

This invention relates primarily to articles composed of fibrous glassand a plastic, and to methods of producing such articles. Morespecifically the invention relates to such articles and methods in whichthe articles involved are composed of an integrated combination of twodistinct fibrous glass and plastic structures in both of which fibrousglass provides dominant characteristics. The invention further relatesto a unique air permeated, plastic bonded, fibrous glass structure ofstress resisting capacity.

The qualities of glass which have made it an outstanding material formany centuries have been its transparency, luster, cheapness ofingredients, and its extraordinary durability. The latter characteristicis of great importance in the applications of glass in its comparativelynew fibrous form. Besides this well known property of glass, glassfibers have proved to possess extreme strength and remarkableresilience.

Breaking strengths of freshly drawn glass fibers have been measured upto 900,000 psi. The elasticity of glass fibers is unique in that theyare perfectly elastic; the stress-strain relationship is a straight lineto ultimate strength. These qualities are astonishing in their highdegree, particularly in view of the common conception of glass asbrittle and rigid.

Broadly considered, fibrous glass has been utilized in two majorfields-as plastic bonded, pervious masses and as combined with plasticin closely compacted bodies. In both, advantage is taken of itsattenuated form, while its chemical inertness is mainly of value in thefirst field and its high strength is of special significance in thesecond.

The original and probably the present principal use for fibrous glass isin comparatively loosely packed masses in which the fibers are closelyassociated in the manner of the cellulose fibers in cotton batting. Abinding agent is ordinarily employed to aid in the coherence of themass. The highest utility of thisform, generally referred to as glasswool, has been in the absorption and resistance to movement of sound,heat and corporeal substances.

Its high competence in insulating or dispersing the travel of sound andheat is derived from the cellular or fine interstitial formationcontaining a great number of minute air pockets. This characteristic ofits structure is also responsible for its effectiveness in filtering airand liquids. The inherent strength and resilience of the glass fibersare more fully relied upon in the use of bonded masses of glass wool incushioning impact or weight stresses In this kind of fibrous glassproduct at least ninety-five percent of the mass usually consists of airspace and the balance comprises glass fibers and the binder. The plasticbinding material rarely exceeds twenty percent by weight of the twocombined materials. This is approximately thirty three percent by volumedue to the wide difference in specific gravities of the two substances.The latter figure relates to the comparative volumes of the glass fibersand the plastic binder and does not take into consideration the aircontent of the mass. The bonded fiber glass mass has a density ofapproximately seven pounds per cubic foot, derived from the weight ofthe glass fibers and plastic, when the proportion of air is ninety-fivepercent.

It is believed that, in general, products of bonded glass wool so farcommercialized have not had a density greater than approximately twentypounds per cubic foot, with air space accounting for about eighty-sixpercent of the total volume.

The second field in which fibrous glass has been most successfullyexploited relates to generally rigid, solid bodies of glass fiberreinforced plastics. Here the strength of the fibrous glass has been thecharacteristic of the greatest value, as it is the factor that enablesthese products to bear tremendous loads. The plastic component providesshape and appearance .and the dielectric property of the plastic is alsoof importance when such solid combinations of glass fibers and plasticsare applied to electrical apparatus.

The proportion of glass fibers in reinforced plastics depends upon thestrength desired in the particular product, but usually lies in therange of twenty to fifty percent, by volume. It is present in thehighest degree in comparatively thin electrical insulating coveringscomposed of fibrous glass fabrics impregnated with plastic.

In fibrous glass reinforced plastic objects there is practically noincorporation of air in contrast to the minimum of eighty-six percent incommercial bodies of bonded glass wool; and the density of reinforcedplastic ordinarily ranges between one hundred, and one hundred and tenpounds per cubic foot compared to the maximum of twenty pounds forproducts of bonded glass wool. While composed of the same two basicmaterials there is this great differentiation in their densities and theproperties derived therefrom.

As set forth, there have been two spaced channels of great activity inproducing articles composed of fiber glass and plastics.

On the one hand, there are the many varied products of fiber glass witha lesser content of plastic binder to hold the glass fibers in a unitaryporous mass containing multiple minute pockets of air and possessingcompressibility and pliancy.

On the other hand, there has been considerable production of generallyrigid, sturdy articles composed of plastic material and glass fiberswith the plastic material usually constituting the major component.These two fields have remained separate and distinct for more than adecade, a very long period in this fast moving industry.

Research people devoting their talents to the development of uses andproducts of glass fibers are highly respected for their advancedthinking and their disregard for traditional practices in venturing intonew fields; surprisingly enough, they have so far overlooked thepossibilities of entering or bridging the wide zone between these twotypes of glass fiber and plastic products. This broad, unexplored zonemay be defined as including all air permeated, plastic bonded fibrousglass masses of densities anywhere between twenty and ninety pounds percubic foot with an air content ranging up to eighty-six percent.

Applicant is, accordingly, deserving of very special recognition forapparently first crossing this sacrosanct barrier and discovering theimpressive usefulness of the air permeated, bonded fibrous glass massesin the broad range so long ignored, and the remarkable utility ofarticles for the first time uniting the physical characteristics andattributes of the two previously diverse product categories.

The principle object of this invention is accordingly to provide fibrousglass and plastic articles of the described dual nature and methods ofproducing such articles.

More specifically, it is the object of the invention to provide panelsof thermal and sound insulating masses of bonded glass fiber withintegral supporting frames, or hangers; impact or weight receivingcushions of glass fiber with integral supporting ribs, frames, or legs;and flotation devices with integrated reinforced portions.

A further object of this invention is to provide a glass fiber andplastic structure of basically cellular or pervious character but havinga density affording strength to the structure for exceeding that ofpreviously created masses of plastic bonded glass wool.

An additional object of the invention is to provide fabricating methodsfor producing articles of the above description.

The purposes of this invention are attained in a preferred manner byhigh densification by compression of selected sections only of masses ofglass fibers containing a plastic bonding agent, and curing the bondingagent while the portions of the mass are held in such densifiedcondition.

Additional methods of securing the objects of the invention, as well asother advantages and benefits thereof, may be better understood from thefollowing description and by referring to the drawings, in which:

FIGURE 1 is a perspective view of a broken section of a batt of glassfibers as cut in rectangular block form from the continuous pack or webcarried by a conveyor from the glass wool forming station;

FIGURE 2 is a perspective view of a rolled blanket of glass wool;

FIGURE 3 is a vertical section of a mold designed for forming acushioned stool blank;

FIGURE 4 is a perspective view of the product of the mold of FIGURE 3;

FIGURE 5 shows an elevation of the cushioned stool shaped from the blankof FIGURE 4;

FIGURE 6 is a perspective view of the lower or male part of a mold forforming, in one operation, a fourlegged stool;

FIGURE 7 is a broken section taken on the line 1818 of FIGURE 6 showingthe plastic impregnated fibrous glass stock in place upon the lower partof the mold and a portion of the upper or female mold in raisedposition;

FIGURE 8 is a section similar to that of FIGURE 18 with the moldsections in closed relation;

FIGURE 9 is a perspective illustration of the stool produced by the moldof the preceding figures;

FIGURE 10 is a vertical section of a mold for creating a flotationdevice such as a life preserver with a blank of glass wool, impregnatedwith a plastic binder, in position to be formed; and

FIGURE 11 is a vertical section of the article produced by the moldillustrated in FIGURE 10.

The glass fibers involved in the products and methods of this inventionare more commonly of a diameter between fifteen and twenty, hundredthousandths of an inch but may have diameters in the range between threeand one hundred, hundred thousandths. Such fine fibers are produced bywell established, very concise, ingenious processes utilizing highpressure steam jets or high velocity, superheated gases to attenuatestreams of molten glass. As these fibers, in various lengths, but seldomsurpassing several inches, drop away from the forming station they arecoated with a binding material discharged from adjacently positionedspray devices.

The fibers fall upon a conveyor and accumulate thereon to a depth usualy in the range of two to eight inches, according to the thicknessdesired, and as controlled by the speed of the conveyor and theproduction rate of the fibers. The continuous blanket or pack of glassfibers travels with the conveyor and ordinarily passes through a bakingoven for setting of the binding agent, which preferably is a phenolformaldehyde resin. However, for purposes of this invention the binderis not set or cured at this stage.

Depending upon the ultimate use for which it is intended the packed webof glass fibers is cut at the discharge end of the conveyor into blocksections 2, such as illustrated in FIGURE 1, or divided into broadstrips 3 and rolled as depicted in FIGURE 2.

Either the block or rolled glass wool stock is adaptable to thisinvention, although the former would be more suitable where it could becut to size or where it would have a thickness not feasible for rolledbatting stock.

In connection with the bonded glass articles described in explaining howthis invention may be practiced, a phenol formaldehyde thermosettingplastic resin would function very satsifactorily as a binding agent. Itis a standard glass fiber binding material and its qualities and mannerof use are well understood. However, once cured, it takes a permanentset and an object in which it is incorporated cannot readily bereshaped. For this reason there may be occasions when the employment ofa thermoplastic binding material would be more advantageous in executingthis invention.

An article and method of fabrication for which a thermoplastic resinwould be suitable are presented in FIG- URES 3, 4 and 5. A polystyreneplastic would presently be recommended for the purpose because of itsvery good, general characteristics, and since its behavior inassociation with glass fibers is comparatively well understood. It maybe sprayed as a water emulsion upon the glass fibers as they fall fromtheir forming station.

The article taken for illustration is a cushioned stool 65 havingpanelled leg members 71. Since the densification and strength of theclosely packed glass fibers require substantial compression in thepreferred manner of practicing this invention, a simpler mold may beutilized if the compression forces may be applied in one direction onlyagainst stock lying generally in a single plane. This would not beadaptable to producing an article having portions extending in variousplanes at extreme angles to each other. However, the benefits of asimple mold are available for producing objects with angled members withthe use of a thermoplastic resin whereby the final shape may be obtainedby reheating and further forming the densified product of the moldingoperation.

As shown in FIGURE 3, the mold 66 is designed to receive a rectangularblank of glass wool 67 impregnated, for example, with twenty-fivepercent by weight, of a polystyrene resin. The batt 67, comprising theblank, is eight inches thick and has a density of four pounds per cubicfoot. Before it may be formed in the mold, the glass fiber batt must beraised to a temperature causing the polystyrene to reach a state ofplasticity. This may be done through preheating or by passing steamthrough cored passages 68 in the mold.

With the polystyrene in its proper fluid condition the mold is closedupon the rectangular glass fiber blank 67. The mold is designed tocompress the portions intended for cushion areas 69 to a thickness oftwo inches and a density of sixteen pounds per cubic foot; and tocondense the narrow sections 70 along the sides of the cushion portionsand the ends 71, ultimately serving as vertical supporting panels, to athickness of one-half inch and a density of sixty-four pounds. The moldis then cooled to solidify the plastic, preparatory to opening of themold and removal of the formed blank.

A plan view of the semi-formed stool is depicted in FIGURE 4. Thesolidified rudimentary leg areas 71 are coplanar with the supportinggrid framing 7-0 which surrounds the cushioning masses 69.

By reheating linear areas indicated at 75 and 76 the polystyrene issoftened and the legs may be turned downward oven stationary dies 78into their functioning vertical position through bending tools 79, asportrayed in FIGURE 5.

In FIGURES 6, 7, 8 and 9 is illustrated a cushioned stool and method offorming it in one molding operation. The male mold part 84 with guidepins and stops 87 is shown in FIGURE 6. It has a truncated pyramidalshape the flat top 85 of which receives the glass fiber stockimpregnated with uncured phenol formaldehyde resin intended to form thepartially cushioned seating surface of the stool. The sloping cornergrooves 86 in which the legs are formed receive more heavilyresin-impregnated fibrous glass.

A vertical section, taken on the diagonal line 18-18 of FIGURE 6,through a corner portion of the male mold part 84 and the correspondingportion of the female mold 88, in raised position, is shown in FIGURE 7.Steam chambers are indicated at 89. The glass fiber stock 90 for thecushioned area is laid in place over the top of the male mold and themore heavily resin impregnated portion 91 of the glass wool is packedinto the corner grooves 86. While wet with the uncured resin, the glassWool will remain momentarily in hand-pressed condensed condition. Thispermits it to be inserted in the groove more snugly and out of the wayof the edges of the female mold when it is brought down to closedposition. The glass stock is then less likely to be squeezed out asundesirable flash or impede closing of the mold.

In FIGURE 8 the mold is illustrated in closed position. The glass fiberstock in the leg areas 93 has been compressed to one-tenth of itsoriginal thickness as has the glass fiber mass disposed in strips 93over the top of the male mold and intended as a grid shaped support forthe cushioned areas 94. The latter are compressed to about one half oftheir original thickness. As a consequence the cushioning bonded fibermass 94 has a density of fourteen pounds per cubic foot, and the legs 93and strengthened grid frame 93 have a density of seventy pounds percubic foot. To provide the highly densified portions with a smootherappearance and to increase their solidarity, additional resin should beapplied by a squeegee, or, the spray nozzle 101 indicated in FIGURE 9.In either case it should "be forced into any open interstices of thesurface. This additional resin may be self curing if of the typecarrying a catalytic agent.

To relieve any tendency of the glass WOOl in the legs to be drawndownwardly by the closing movement of the molds the female mold has acut away portion 92 into which glass fiber stock is received to form asmall foot 97 at the base of the leg. Due to the nature of the moldingoperation, projecting corners 96 are present at the sides of the top ofeach leg. These may be cut off to give a smoother appearance asindicated at 95.

In FIGURES and 11 a manner of utilizing the principles of the inventionin creating an article with a protective shell is illustrated. Theobject used as an example is a life preservor. The interior of such aflotation article should of course be composed of a most buoyantsubstance, while the exterior should be strong enough to hold the shapeof the article and resist blows to which it may be subjected.

'In FIGURE 10 is shown the shaping mold with a square cornered ring ofresin impregnated, glass W001 114, preferably of a density between oneand two pounds, in place between the upper and lower halves, 104 and105, of the mold. Steam cores are indicated at 106 and platens at 108and 109. Closing of the mold by ram 111 brings the glass wool blank 114into the conventional rounded life preserver shape 115 shown in FIGURE11. Then a heavy coating of additional resin is applied over the surfaceof the life preserver by use of the spray device 118. This resin is thenforced into the outer interstices of the bonded glass fibers with asqueegee. This coating 116 is subsequently hardened in a curingtreatment and provides the fluffily packed interior 117 with a sturdyprotective shell.

Reference herein has been restricted to phenol formaldehyde andpolystyrene plastics as they are considered best known, asrepresentative of thermosetting and thermoplastic resins, by techniciansin the fibrous glass industry. Other plastic resins are quite adaptableto this invention and may have advantages under certain conditions. Forinstance, the therm-osetting epoxy resins would be superior to phenolformaldehyde under curing of heavy sections as they do not release gasesand extraneous matter. Other examples could involve the betterelectrical properties of polyesters, and melamines. Therefore it is notdesired to limit the scope of this invention to any particular plasticcomponent.

While the disclosure has presented articles with various shapes ofdensified strengthened sections, there are many alternate forms whichwould lend themselves to the practice of this invention and would comewithin its scope.

Likewise certain specific densities have been cited in describing theembodiments disclosed herein. It should be realized that the densitiesinvolved are somewhat rela tive in that a flufiy stock of bonded glassfibers may be held for light duty by a strengthened section of quite lowdensity, while an article for liquid filtering or impact cushioningwould require an integrated supporting section of considerabledensification and sturdiness.

In conclusion it may be well to summarize the salient points of noveltybelieved to reside in the subject matter of this application.

The board inventive themes are carried into the stools presented inFIGURES 5 and 9. The first is generally similar, in having portions ofcontrasting densities, to preceding articles with the substitution of athermoplastic resin for the more standard phenol formaldehyde.

The stool of FIGURE 9 is an article not easily formed with straightcompression so utilization is made of extra loading of plastics inportions to be relied upon for support. It also has a toughened outerlayer obtained by the application of additional resin after the formingoperation.

The flotation device of FIGURE 11 is illustrative of an articleembodying this invention in which the strengthened area constitutes ashell for a lightly packed inner mass.

The fundamental method of producing articles devised by applicant is thecompression of certain areas of a mass of fiber glass carrying anuncured resin binder to bring about, upon curing of the res-in, a muchgreater densification in the certain areas as compared with that of thebalance of the mass.

A closely allied method is that utilized in producing the new, airpermeated, strength providing structures, wherein a mass of resinimpregnated glass fibers is compressed to a point where the resinbridges between substantial portions of the lengths of the fibers, withentrained air pockets of reduced quantity and size, and the resin iscured While the mass is so compressed.

Collateral methods relate to the producing of an article having acomparatively loose core and a sturdy outer shell, the utilization of athermoplastic, and lesser steps taken in the creation of the variousembodiments.

As may be concluded from the preceding, applicant has accomplished theobjects of his invention through the creation of new structures of airpermeated, plastic bonded glass fibers; providing articles of plasticand fibrous glass of multiple densities and function; and through theprovision of methods for producing such structures and articles.

I claim:

1. A composite, integrate-d, non-planar, movable, independentlyserviceable article of fibrous glass and a resinous material havingdistinct sections of different structural and utility characteristics,said sections including a section of low density, with a preponderantair content, in which the fibrous glass is generally held in spacedrelation by a binder of resinous material, and a sturdy, semi-solidsection of high density with a substantially continuous andvolumetrically preponde-rant component of resinous material, which isreinforced with fibrous glass.

2. An independent, movable structure having an air permeated, resilient,low density first portion of resin bonded, discontinuous and randomlypositioned glass fibers, said first portion being generally homogeneousin relative content of resin and glass fibers, and a rigid,smooth-surfaced, substantially impervious second portion integral withsaid first portion, said second portion being principally of a resinouscomposition reinforced by glass fibers extending therein from said firstportion.

References Cited UNITED STATES PATENTS 2,244,912 6 1941 Kollander297-461 X 3,113,788 12/1963 Johnston 280150 3,150,032 9/1964 Rubenstein161-461 3,164,110 1/1965 Bofinger 108161 CASMIR A. NUMBERG, PrimaryExaminer.

1. A COMPOSITE, INTEGRATED, NON-PLANAR, MOVABLE, INDEPENDENTLYSERVICEABLE ARTICLE OF FIBROUS GLASS AND A RESINOUS MATERIAL HAVINGDISTINCT SECTIONS OF DIFFERENT STRUCTURAL AND UTILITY CHARACTERISTICS,SAID SECTIONS INCLUDING A SECTION OF LOW DENSITY, WITH A PREPONDERANTAIR CONTENT, IN WHICH THE FIBROUS GLASS IS GENERALLY HELD IN SPACEDRELATION BY A BINDER OF RESINOUS MATERIAL, AND A STURDY, SEMI-SOLIDSECTION OF HIGH DENSITY WITH A SUBSTANTIALLY CONTINOUS ANDVOLUMETRICALLY PREPONDERANT COMPONENT OF RESINOUS MATERIAL, WHICH ISREINFORCED WITH FIBROUS GLASS.